臺灣博碩士論文加值系統

本論文主要是建立以近場方式照射散射金屬導體﹐於遠場以多頻率、多角度之掃瞄技術﹐擷取散射場資料﹐並據以微波成像之理論、方法和實驗量測。
理論分析證明﹐當散射導體滿足物理光學近似﹐且以近場照射及遠場接收的形式﹐利用多頻率、多角度掃瞄技術﹐擷取散射導體的傅氏空間資料﹐若直接經由反傅利葉轉換﹐無法和以遠場照射及遠場接收的情形一樣﹐可以直接重建該散射導體的微波影像於 空間。但若在遠場的觀測角度很小之假設﹐及量測頻寬相對於中心頻率相當小之近似下﹐所量測之多頻率、多角度散射場資料﹐由反傅利葉轉換﹐得到之散射導體影像﹐須經一非線性座標轉換﹐如此才可正確的重建散射導體之微波影像。
論文中並建立一近場照射之微波成像實驗系統﹐用以量測金屬物體之多頻率、多角度遠場散射資料。量測的散射導體有四種不同的形式﹐包含兩根細金屬圓柱、金屬板、單一金屬圓柱體以及複雜形狀之B-52模形飛機。藉由上述方法重建之微波影像﹐均相當符合散射導體的幾何形狀。

In this thesis﹐the principle﹐methodology and experiment of microwave imaging of conductive object under the near field illumination and far field receiving are presented.
Under the assumptions of physical optics approximation﹐analytical results show that the image of the scattering object with the near field illuminating and far field receiving cannot be directly reconstructed using the Fourier inversion of the object Fourier space data recorded in space by the multi-frequency and multi-aspect technique as that for the way far field illuminating and far field receiving. However﹐as the observation angle becomes small and the bandwidth is small relative to the center frequency, the Fourier inversion of the recorded data gives an image in (u, y) space. By using an unlinear transformation between u and x﹐the image in the correct (x, y) space can be reconstructed.
A microwave imaging measurement system based on the near field illuminating and far field receiving is developed to record the object scattered field using the multi-frequency and multi-aspect technique. Images of four different types of scattering objects﹐include two thin cylinders﹐a metallic plate﹐a metallic cylinder and a 1:72 B-52 scaled airplane model, are reconstructed using the developed microwave imaging system. Results of simulation and experiment are shown in good agreement with the scattering object geometries.

第一章 簡介…………………………………………..………………1
1.1 微波影像.………………………………………………………1
1.1.1 反合成孔徑雷達技術……………………………………...1
1.1.2 天線合成孔徑雷達技術……………………………………2
1.2 章節內容概述…………………………………………………...3
第二章 遠場照射遠場接收之微波成像方法…………………..……5
2.1 散射場公式………….…………………………………………5
2.2 成像方法…………………………………………………….…8
2.2.1 Bojarski恆等式……………………………………….…8
2.2.2 傅利葉轉換法………………………………..………….12
2.3 Ewald球及影像解析度………………………………………14
2.3.1 Ewald球之分佈情形…………………………………….14
2.3.2 有限頻寬重建影像之解析度……………………….…..15
第三章 近場照射遠場接收之微波成像方法…………………..……25
3.1 散射場公式………………………………………………..…...25
3.1.1 號角天線於H-平面之幅射場型…………………………26
3.1.2 離散點狀導體之散射場…………………………… ……32
3.1.3 連續形狀散射導體之散射場……………………………..34
3.2 成像方法………………………………………………………36
3.2.1 離散點狀散射導體之成像方法…………………………..36
3.2.2 連續形狀散射導體之成像方法…………………………..39
3.3 Ewald球之分佈及解析度……………………………………...40
3.3.1 Ewald球之分佈情形……………………………………...40
3.3.2 有限頻寬資料重建影像之解析度……………………….41
第四章 數值模擬與實驗結果………………………………………..49
4.1 數值模擬結果…………………………………………………..49
4.1.1 離散線狀導體…………………………………………….49
4.1.2 連續形狀導體…………………………………………….50
4.2 實驗量測裝置………………………………………………….52
4.2.1 微波量測系統…………………………………………….52
4.2.2 HPVEE視效程式……………………………………….….53
4.3 實驗校準方法………………………………………………….56
4.4 實驗結果……………………………………………………….58
第五章 結論………………………………………………………….91
附錄一 控制實驗量測系統之HPVEE視效程式…………………….93
參考文獻………………………………………………………………

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